Someone's using my email?

[Vendetta]

On sites like Twitter when you register an account, you have to verify the email but there is a very easy way to bypass this.

I would say your account has not been hacked (but it is better to make sure). I believe a spammer has probably set up an account with that email and bypass the verify so Twitter believes the email to actually be the spammers.

You should also contact Twitter to explain the problem with them and they will look in to it and hopefully close the account that is using your email.